A123848 Number of ways to build a contiguous building with n LEGO blocks of size 5 X 5 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.

1, 29, 57, 1955, 5805, 222291, 694961

Offset

1,2

Comments

The base block is not counted among the n and must be the only block in the bottom layer of the building.

Links

Table of n, a(n) for n=1..7.

M. Abrahamsen and S. Eilers, On the asymptotic enumeration of LEGO structures, Exper Math. 20 (2) (2011) 145-152.

B. Durhuus and S. Eilers, On the entropy of LEGO, arXiv:math.CO/0504039

Crossrefs

Sequence in context: A339865 A033915 A192358 * A340669 A040812 A184081

Adjacent sequences: A123845 A123846 A123847 * A123849 A123850 A123851

Keyword

nonn,more

Author

Søren Eilers, Oct 29 2006

Status

approved